Threaded Structures with Solder Control Features

ABSTRACT

Threaded standoff structures may be provided with features that control the flow of solder. A base structure for a standoff may be formed from a solderphobic material such as brass. A through hole may be formed in the base structure. The base structure may be coated with a solderphilic material such as an inner layer of nickel and an outer layer of tin. A tapping tool may be used to remove the solderphilic material from the opening by tapping threads into the opening, thereby exposing the underlying base metal of the standoff in the opening. During attachment to a substrate such as a printed circuit board, the standoff may be exposed to molten solder. The solderphilic coating on the outer surface of the standoff may attract the molten solder, whereas the solderphobic base metal in the threaded opening may help prevent solder from contaminating the threads in the opening.

BACKGROUND

This relates generally to mechanical structures, and, more particularly,to threaded structures such as threaded standoffs for use in assemblingelectronic devices.

Threaded structures such as threaded standoffs are often used inassembling electronic devices. For example, a threaded standoff may beused in attaching a component to a printed circuit board.

Standoffs are often attached to printed circuit boards using solder. Ifcare is not taken, molten solder can wick onto portions of the threadsin a standoff. This can make it difficult or impossible to insert ascrew into the standoff.

It would therefore be desirable to be able to provide improvedstructures such as improved standoffs and other threaded structures thatare exposed to solder.

SUMMARY

Threaded structures such as threaded standoff structures may be providedwith features that control the flow of solder. The features may includesolderphobic and solderphilic surface regions.

A base structure for a standoff may be formed from a solderphobicmaterial such as brass. An opening may be formed in the base structure.The standoff may be coated with a solderphilic coating such as an innerlayer of nickel and an outer layer of tin. The solderphilic coating maybe formed on an interior surface and an exterior surface of thestandoff. A tapping tool may be used to remove the solderphilic coatingfrom the interior surface of the standoff by tapping threads into thestandoff opening. Removing the solderphilic coating from the interiorsurface may expose the solderphobic base metal of the standoff in theopening.

During attachment of the standoff to a substrate such as a printedcircuit board, the standoff may be exposed to molten solder. Thesolderphilic coating on the exterior surface of the standoff may attractthe molten solder, thereby securing the standoff to the substrate. Theexposed solderphobic base metal in the threaded opening may help preventsolder from contaminating the threads in the opening, thereby allowing ascrew to be fully inserted into the threaded opening.

Further features of the invention, its nature and various advantageswill be more apparent from the accompanying drawings and the followingdetailed description.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view of an illustrative electronic device suchas a laptop computer with electronic device structures that may beassembled using threaded standoffs in accordance with an embodiment ofthe present invention.

FIG. 2 is a perspective view of an illustrative electronic device suchas a handheld electronic device with electronic device structures thatmay be assembled using threaded standoffs in accordance with anembodiment of the present invention.

FIG. 3 is a perspective view of an illustrative electronic device suchas a tablet computer with electronic device structures that may beassembled using threaded standoffs in accordance with an embodiment ofthe present invention.

FIG. 4 is a cross-sectional side view of an illustrative electronicdevice with electronic device structures that may be assembled usingthreaded standoffs in accordance with an embodiment of the presentinvention.

FIG. 5 is a cross-sectional side view of a conventional standoff thathas been exposed to molten solder during the process of mounting thestandoff to a printed circuit board.

FIG. 6 is a cross-sectional side view of a standoff with solderphobicthreads in accordance with an embodiment of the present invention.

FIG. 7 is a diagram of an illustrative deposition tool that maybe usedto coat a standoff in accordance with an embodiment of the presentinvention.

FIG. 8 is a diagram of an illustrative electroplating tool that maybeused to coat a standoff in accordance with an embodiment of the presentinvention.

FIG. 9 is a diagram of an illustrative machining tool that maybe used toform an opening in a standoff in accordance with an embodiment of thepresent invention.

FIG. 10 is a diagram of an illustrative tapping tool that maybe used tocut threads in the opening of a standoff in accordance with anembodiment of the present invention.

FIG. 11 is a diagram showing illustrative steps involved in forming astandoff with solderphobic threads and a solderphilic exterior surfacein accordance with an embodiment of the present invention.

DETAILED DESCRIPTION

Structures such as metal fasteners and other structures are often usedin assembling printed circuit boards, electronic components, connectors,and other structures associated with an electronic device. For example,threaded structures such as threaded standoffs, threaded bosses, andthreaded nuts may be used in attaching one or more structures togetherin an electronic device.

Threaded structures such as threaded standoffs may be mounted to asubstrate such as a printed circuit board. Threaded standoffs may, forexample, be soldered to solder pads on the surface of a printed circuitboard. Threaded standoffs may be provided with solder control featuressuch as solderphilic surfaces and solderphobic surfaces.

Illustrative electronic devices that may be provided with threadedstructures having solder control features are shown in FIGS. 1, 2, and3. FIG. 1 shows how electronic device 10 may have the shape of a laptopcomputer having upper housing 12A and lower housing 12B with componentssuch as keyboard 16 and touchpad 18. Assemblies such as printed circuitboards having threaded engagement structures may be mounted within upperhousing 12A and/or lower housing 12B.

FIG. 2 shows how electronic device 10 may be a handheld device such as acellular telephone, music player, gaming device, navigation unit, orother compact device. In this type of configuration for device 10,housing 12 may have opposing front and rear surfaces. Display 14 maymounted on a front face of housing 12. Display 14 may, if desired, havea display cover layer or other exterior layer that includes openings forcomponents such as button 36 and speaker port 38. Assemblies such asprinted circuit boards having threaded engagement structures may bemounted within housing 12.

FIG. 3 shows how electronic device 10 may be a tablet computer. Inelectronic device 10 of FIG. 3, housing 12 may have opposing planarfront and rear surfaces. Display 14 may be mounted on the front surfaceof housing 12. As shown in FIG. 3, display 14 may have a cover layer orother external layer with an opening to accommodate button 36.

The configurations for device 10 shown in FIGS. 1, 2, and 3 are merelyillustrative. In general, electronic device 10 may be a laptop computer,a computer monitor containing an embedded computer, a tablet computer, acellular telephone, a media player, or other handheld or portableelectronic device, a smaller device such as a wrist-watch device, apendant device, a headphone or earpiece device, or other wearable orminiature device, a television, a computer display that does not containan embedded computer, a gaming device, a navigation device, an embeddedsystem such as a system in which electronic equipment with a display ismounted in a kiosk or automobile, equipment that implements thefunctionality of two or more of these devices, or other electronicequipment.

Device 10 may have a housing enclosure such as housing 12. Housing 12,which is sometimes referred to as a case or enclosure, may be formed ofmaterials such as plastic, glass, ceramics, carbon-fiber composites andother composites, metal, aluminum, other materials, or a combination ofthese materials. Device 10 may be formed using a unibody construction inwhich most or all of housing 12 is formed from a single structuralelement (e.g., a piece of machined metal or a piece of molded plastic)or may be formed from multiple housing structures (e.g., outer housingstructures that have been mounted to internal frame elements, weldedstandoffs, engagement structures, engagement member receivingstructures, or other internal housing structures).

Device 10 may have one or more displays such as display 14. Display 14may be a liquid crystal display, an organic light-emitting diode (OLED)display, or other suitable display. Display 14 may include displaypixels formed from light-emitting diodes (LEDs), organic light-emittingdiodes (OLEDs), plasma cells, electronic ink elements, liquid crystaldisplay (LCD) components, and/or other suitable display pixelstructures. Display 14 may, if desired, include capacitive touch sensorelectrodes for a capacitive touch sensor array or other touch sensorstructures (i.e., display 14 may be a touch screen).

As shown in FIG. 4, device 10 may include electronic components such asprinted circuit board 22 and components 40. Components 40 may includeintegrated circuits or other circuit components, batteries, cameras,compasses, wireless communications circuits, antennas, circuit boardconnectors such as board-to-board connectors or other circuitry.Components 40 may be mounted on top surface 22T and/or bottom surface22B of printed circuit board substrate 22.

Printed circuit board 22 and components 40 may be used to run softwarecode for device 10, such as internet browsing applications,voice-over-internet-protocol (VOIP) telephone call applications, e-mailapplications, media playback applications, operating system functions,antenna and wireless circuit control functions, etc.

Printed circuit board 22 and components 40 may be used in implementingsuitable communications protocols. Communications protocols that may beimplemented using printed circuit board 22 and components 40 includeinternet protocols, wireless local area network protocols (e.g., IEEE802.11 protocols—sometimes referred to as Wi-Fi®), protocols for othershort-range wireless communications links such as the Bluetooth®protocol, protocols for handling cellular telephone communicationsservices, etc.

Printed circuit board 22 may include one or more layers of dielectricand one or more layers of conductor. Printed circuit board 22 may, forexample, be a rigid printed circuit board formed form a material such asfiberglass-filled epoxy (e.g., FR4), may be a flexible printed circuitformed from materials such as polyimide (sometimes referred to as a“flex circuit”), or may be formed from other suitable materials orcombinations of these materials.

If desired, device 10 may be provided with a structural member such ascowling 24. Some of components 40 may be mounted between printed circuitboard 22 and cowling 24. Cowling 24 may be mounted on top of one or moreprinted circuit board connectors. For example, cowling 24 may befastened over first and second mating connectors and may help hold thefirst and second mating connectors together. Printed circuit boardconnectors may be used in connecting printed circuit board 22 to otherprinted circuits in device 10 such as a flex circuit.

As shown in FIG. 4, device 10 may include threaded structures such asstandoffs 28. Standoffs 28 may be soldered to solder pads on the surfaceof printed circuit board 22. Standoffs 28 may have threads that receivecorresponding threaded screws such as screws 32. Standoffs 28 and screws32 may be used to assemble structures such as shielding cans, cowlings,housing members, connector structures, and other electronic devicestructures. In the illustrative configuration shown in FIG. 4, eachscrew 32 may pass through a hole in cowling 24 and may be received by athreaded opening in standoff 28, thereby attaching cowling 24 to printedcircuit board 22.

Threaded structures such as standoffs 28 may be used in assembling anysuitable structures. The example of FIG. 4 in which standoffs 28 areused in mounting cowling 24 to printed circuit board 22 over components40 is merely illustrative.

FIG. 5 is a cross-sectional side view of a conventional standoff mountedto a printed circuit board. As shown in FIG. 5, standoff 280 includesthreaded opening 460 in brass body 500. Brass body 500 is coated withsolderphilic coating 480. Coating 480 includes an inner nickel layer andan outer tin layer. When standoff 280 is mounted to metal pad 420 onprinted circuit board 220, molten solder 520 is attracted to the tin incoating 480. This causes some of solder 520 to wick upwards in region490 on the outer surface of standoff 280. The presence of thesolderphilic tin layer on the surface of the threads in threaded opening460 also tends to cause solder 520 to wick upwards and over some of thethreads in opening 460, as shown by wicked solder portion 440 at thebase of opening 460. The presence of solder portion 440 over the threadsin standoff 280 can make it difficult or impossible to properly insert ascrew into opening 440.

A standoff having a configuration that can help avoid soldercontamination in the threaded opening is shown in FIG. 6. As shown inthe cross-sectional side view of FIG. 6, standoff 28 may be mounted onmetal pad 42 (sometimes referred to as a solder pad) on printed circuitboard 22 using solder 52. To prevent solder from wicking over thethreads in threaded opening 78, threaded opening 78 may be provided witha solderphobic surface (interior surface 54), whereas the remainder ofstandoff 28 (e.g., exterior surface 56) may be coated with asolderphilic coating such as solderphilic coating 48.

Surface 54 may be formed by exposing solderphobic brass from basestructure 50. Surface 56 may be formed by coating base structure 50 withsolderphilic coating 48. Solderphilic coating 48 may, for example,include an inner layer of nickel and an outer layer of tin. Solderphiliccoating 48 may attract solder 52 more strongly than solderphobic surface54.

During soldering operations, solder portion 58 may wick up and over thesolderphilic outer surface on the sides of standoff 28 and may wickalong the solderphilic outer surface on the bottom of standoff 28,thereby securely mounting standoff 28 to printed circuit board 22. Atthe same time, solderphobic surface 54 may help prevent solder 52 fromwicking onto threads in lower region 60 of opening 78.

Any suitable manufacturing equipment may be used to form threadedstructures such as threaded standoff member 28 of FIG. 6. As shown inFIG. 7, coatings such as solderphilic metal coatings may be deposited onthe surface of standoff 28 using deposition tool 62. Deposition tool 62may deposit coating materials 64 from source 66. Deposition tool 62 mayuse evaporation, sputtering, spraying, dipping, or other physical vapordeposition techniques in applying coatings to standoff 28. Depositiontool 62 may also use chemical vapor deposition techniques and othertechniques for applying coatings to standoff 28, if desired.

As shown in FIG. 8, electrochemical deposition techniques may be used incoating standoff 28. For example, electroplating tool 70 may be used incoating standoff 28 with metal layers. During coating, standoff 28 maybe lowered in direction 74 until some or all of standoff 28 is immersedin electroplating bath 76 in electroplating vessel 68. If desired,electroplating tool 70 may first plate standoff 28 with an inner layerof nickel and may subsequently plate standoff 28 with an outer layer oftin.

FIG. 9 shows how standoff 28 may be machined using machining tool 82.Machining tool 82 may have drill bits or other bits such as bit 80.Motor 72 may rotate bits such as bit 80 to drill openings such asopening 78 in standoff 28. Machining tool 82 may include stamping toolsand other tools that form parts into desired shapes using pressure,laser cutting tools, plasma cutting tools, etc.

The example of FIG. 9 in which a machining tool is used to form anopening in standoff member 28 is merely illustrative. If desired,standoff member 28 may be provided with an opening during an initialmanufacturing process. For example, base structure 50 (FIG. 6) may beformed from a casting process in which liquid metal is poured into amold. The mold may have a hollow cavity shaped such that the resultingsolidified part has an opening (e.g., a through hole such as throughhole 78 of FIG. 6).

FIG. 10 shows how standoff 28 may be threaded using tapping tool 84.Tapping tool 84 may have a tap such as tap 86. Motor 88 may rotate tap86 to cut threads on interior surface 54 of standoff 28. In addition toforming threads in opening 78, tapping tool 84 may also be used toremove coatings such as solderphilic metal coatings from interiorsurface 54 (e.g., tapping tool 84 may be used to cut threads in opening78 while simultaneously exposing the base material that forms standoff28).

With one suitable arrangement, standoff 28 may be formed using anapproach of the type shown in FIG. 11. As indicated by arrow 90,standoff 28 may initially be a solid part with no openings or holes, asshown by solid base portion 50. Base portion 50 may be formed from asolderphobic material such as brass or other solderphobic materials(e.g., solderphobic metals).

As indicated by arrow 92, opening 78 may be formed in base portion 50using machining tools such as machining tool 82. As shown in FIG. 11,interior surface 54 may initially be planar or substantially planar(e.g., opening 78 may initially be formed without threads).

As indicated by arrow 94, base portion 50 may be coated with asolderphilic coating such as coating 48 (e.g., an inner layer of nickelfollowed by an outer layer of tin or other suitable metals). Coatingtools 98 may be used in forming solderphilic coating 48 on the surfaceof base structure 50. Coating tools 98 may include, for example,deposition tool 62 of FIG. 7 or plating tool 70 of FIG. 8. As shown inFIG. 11, all or substantially all of the surface of base portion 50 iscoated with solderphilic coating 48 (e.g., coating 48 is formed on bothinterior surface 54 and exterior surface 56 of standoff 28).

As indicated by arrow 96, threads may be cut on interior surface 54 ofstandoff 28 using tapping tools such as tapping tool 84. Cutting threadson surface 54 may also remove solderphilic coating 48 from surface 54,thereby exposing base portion 50 in opening 78. Because the tappingprocess exposes the brass material that makes up base 50, the threads ofthreaded inner surface 54 of standoff 28 may be solderphobic and mayhelp prevent solder from contaminating threads in opening 78. Incontrast, solderphilic coating 48 on exterior surface 56 may encouragesolder 52 to wick under the lower surface of standoff 28 and up theedges of standoff 28 to assist in forming a satisfactory bond withsolder pad 42 on printed circuit board 22 (FIG. 6) during assembly.

The foregoing is merely illustrative of the principles of this inventionand various modifications can be made by those skilled in the artwithout departing from the scope and spirit of the invention.

What is claimed is:
 1. A method for forming a threaded standoffcomprising: with a machining tool, forming an opening in a basestructure; with a coating tool, coating a surface of the base structurewith a solderphilic coating; and with a tapping tool, forming threads inthe opening while removing the solderphilic coating from the opening. 2.The method defined in claim 1 wherein the solderphilic coating comprisesa material selected from the group consisting of: tin and nickel, andwherein removing the solderphilic coating from the opening comprisesremoving the material from the opening.
 3. The method defined in claim 1wherein the base structure comprises brass and wherein coating thesurface of the base structure with the solderphilic coating comprisescoating the brass with the solderphilic coating.
 4. The method definedin claim 1 wherein the coating tool comprises a deposition tool, whereinthe solderphilic coating comprises metal, and wherein coating thesurface of the base structure with the solderphilic coating comprisesdepositing the metal on the surface of the base structure with thedeposition tool.
 5. The method defined in claim 1 wherein the coatingtool comprises an electroplating tool, wherein the solderphilic coatingcomprises metal, and wherein coating the surface of the base structurewith the solderphilic coating comprises electroplating the metal on thesurface of the base structure with the electroplating tool.
 6. Themethod defined in claim 1 wherein the base structure comprises brass andwherein removing the solderphilic coating from the opening comprisesremoving the solderphilic coating to expose the brass within theopening.
 7. The method defined in claim 1 wherein the base structure isformed from a first material, wherein the solderphilic coating is formedfrom a second material, wherein the second material attracts solder morestrongly than the first material, and wherein removing the solderphiliccoating from the opening comprises removing the second material toexpose the first material in the opening.
 8. A method for forming athreaded standoff comprising: forming an opening in a standoff member;with a coating tool, coating a surface of the standoff member with asolderphilic coating; and removing the solderphilic coating from theopening by forming threads in the opening with a tapping tool.
 9. Themethod defined in claim 8 wherein the solderphilic coating comprises amaterial selected from the group consisting of: tin and nickel, andwherein coating the surface of the standoff member with the solderphiliccoating comprises coating the surface of the standoff member with thematerial.
 10. The method defined in claim 8 wherein the standoff membercomprises brass and wherein removing the solderphilic coating from theopening comprises removing the solderphilic coating to expose the brassin the opening.
 11. The method defined in claim 8 wherein the standoffmember comprises an interior surface and an exterior surface, whereinthe interior surface defines the opening, and wherein coating thesurface of the standoff member with the solderphilic coating comprisescoating the interior surface and the exterior surface with thesolderphilic coating.
 12. The method defined in claim 8 wherein formingthe opening in the standoff member comprises drilling the opening in thestandoff member with a machining tool.
 13. The method defined in claim 8wherein coating the surface of the standoff member with the solderphiliccoating comprises coating the surface of the standoff member with thesolderphilic coating after forming the opening in the standoff member.14. The method defined in claim 8 wherein the coating tool comprises adeposition tool, wherein the solderphilic coating comprises metal, andwherein coating the surface of the standoff member with the solderphiliccoating comprises depositing the metal on the surface of the standoffmember using the deposition tool.
 15. The method defined in claim 8wherein the coating tool comprises an electroplating tool, wherein thesolderphilic coating comprises metal, and wherein coating the surface ofthe standoff member with the solderphilic coating compriseselectroplating the standoff member with the metal using theelectroplating tool.
 16. The method defined in claim 8 wherein thestandoff member is formed from a first material, wherein thesolderphilic coating is formed from a second material, wherein the firstmaterial repels solder more strongly than the second material, andwherein removing the solderphilic coating from the opening comprisesremoving the second material to expose the first material in theopening.
 17. A method for forming a threaded standoff that has asolderphilic surface that is configured to receive solder when attachingthe threaded standoff to a solder pad and that has a threaded openingthat is configured to receive a screw, the method comprising: forming anopening in a metal standoff member; forming the solderphilic surface bycoating the metal standoff member with a solderphilic coating; andremoving the solderphilic coating within the opening to exposeunderlying metal of the metal standoff member by tapping threads intothe metal standoff member in the opening.
 18. The method defined in 17wherein the underlying metal comprises a solderphobic material andwherein removing the solderphilic coating within the opening comprisesremoving the solderphilic coating to expose the solderphobic material inthe opening.
 19. The method defined in claim 17 wherein the solderphiliccoating comprises an inner layer of nickel and an outer layer of tin andwherein forming the solderphilic surface comprises coating the metalstandoff member with the inner layer of nickel and the outer layer oftin.
 20. The method defined in claim 17 wherein forming the opening inthe metal standoff member comprises machining the opening in the metalstandoff member with a machining tool before forming the solderphilicsurface.